An inflator for inflating a vehicle occupant protection device, such as an air bag, may contain a body of ignitable gas generating material. The gas generating material is ignited when the vehicle experiences a collision for which inflation of the air bag is desired to protect an occupant of the vehicle. As the gas generating material burns, it generates a large volume of inflation gas which is directed to flow from the inflator into the air bag to inflate the air bag. When the air bag is inflated, it extends into the vehicle occupant compartment to help protect an occupant of the vehicle from a forceful impact with parts of the vehicle.
Such an inflator commonly has an elongated cylindrical housing. A tubular structure is contained in the housing. The tubular structure defines an elongated cylindrical combustion chamber in which the body of gas generating material is contained, and includes a tubular filter. The filter cools and filters the gas as the gas flows radially outward through the filter from the combustion chamber toward the housing. A plurality of gas outlet openings extending through the housing direct the gas to flow radially outward from the inflator toward the air bag.
The body of gas generating material has approximately the same size and shape as the cylindrical combustion chamber. The body of gas generating material thus has an elongated cylindrical shape with longitudinally opposite ends adjacent to the opposite ends of the combustion chamber. Moreover, the elongated body of gas generating material is defined by a plurality of separate, shorter cylindrical grains of gas generating material.
The housing may also contain a spring at one end of the elongated body of gas generating material. Such a spring exerts a spring force axially against the elongated body of gas generating material to hold the separate grains of gas generating material together in a row extending along the length of the combustion chamber.